Porous composites with high-aspect ratio crystals

ABSTRACT

The present disclosure is directed toward composite materials comprising high aspect ratio habits of drug crystals which can be partially or fully extending into a substrate, and additionally, can be projecting from a substrate at an angle of about 20° to about 90°. The present disclosure is directed toward medical devices, such as medical balloons, comprising said composite and methods of using and making the same. The described composite can be used for the local treatment of vascular disease. The present disclosure is also directed toward paclitaxel crystals with a hollow acicular habit.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.14/210,162, filed Mar. 13, 2014, now U.S. Pat. No. 11,167,063, issuedNov. 9, 2021, which claims the benefit of U.S. Provisional Application61/786,244, filed Mar. 14, 2013, which are incorporated herein byreference in their entireties for all purposes.

FIELD OF THE DISCLOSURE

The disclosure relates to composites comprising substrates havingoriented drug crystals of high aspect ratio habit. In particular, thedisclosure relates to said composites, their methods of preparation,devices comprising said composites, and their methods of use, e.g., usesfor the treatment of vascular disease. The disclosure also relates tohollow, high aspect ratio paclitaxel crystals.

BACKGROUND OF THE DISCLOSURE

Vascular diseases, such as arthrosclerosis, artery occlusion, andrestenosis, are a leading cause of human mortality and morbidity.Vascular diseases arise from a variety of causes, and in some cases,necessitate surgical or endovascular intervention. Trauma to thevascular system can also necessitate surgical intervention to treat thetraumatized anatomy. A common treatment for vascular disease is theshort-term or long-term contact of a tissue with an endovascular medicaldevice, such as a balloon or a stent, respectively, that is coated witha drug that prevents or reduces vascular disease at the site of contact.Upon contact of the endovascular medical device with a diseased vasculartissue, the drug elutes from the endovascular medical device into thesurrounding tissue at the site of contact, thereby treating the vasculardisease at a local, rather than systemic, level. The long-term contact,e.g., implantation, of endovascular medical devices including vasculargrafts, stent-grafts, and stents, and the short-term contact of vascularmedical devices including catheter-based balloons, are often undertakento treat vascular diseases and vascular trauma.

Additional vascular diseases or vascular trauma that can requiresurgical or endovascular intervention include, but are not limited to,vascular injury, vascular prophylactic intervention, phlebitis, intimalhyperplasia, vulnerable plaques, carotid plaques, coronary plaque,vascular plaque, peripheral plaque, aneurismal disease, vasculardissections, atherosclerotic plaques, atherosclerotic lesions, vascularinfection, stenosis, restenosis, and vascular sepsis.

The treatment of vascular disease at a local, rather than systemic,level is often preferred. Systemic administration of drugs can produceunwanted side effects, when compared to the local administration of adrug to a target tissue to treat vascular disease. The utilization of adrug-coated endovascular medical device has become a standard techniquein the treatment of vascular disease.

Drug eluting balloons (DEBs) are one example of a drug-coatedendovascular medical device. The literature discloses the use of DEBsfor the treatment of vascular diseases, including coronary arterydisease and peripheral artery disease (see e.g., U.S. Pat. No.5,102,402, issued to Dror et al.). Dror et al. disclose placing a DEB ina blood vessel lumen to treat the vessel wall, inflating the balloon,and contacting the balloon surface with the luminal vessel wall todeliver a drug into the blood vessel wall. The dosing of the drug to thetreatment site using DEBs can be highly variable and unpredictableimmediately after implantation, and local drug levels in the vasculartissue can be highly variable and unpredictable over an extended time.It is therefore desirable to have improved implantable medical devicesand methods for treating vascular disease that are reliable andreproducible in drug dosing.

Drugs that are used to treat vascular disease include antiproliferative,antiplatelet, or anticoagulant drugs. One example of anantiproliferative drug for the treatment of vascular disease, via itselution from a coated endovascular medical device, is paclitaxel.

Paclitaxel is a small molecule originally isolated from the needles andbark of the Pacific Yew tree (Taxus brevifolia). Paclitaxel has provenparticularly successful for the treatment of vascular disease via itsrelease from a coated endovascular medical device. Paclitaxel's role inthe treatment of vascular disease is due to its ability to bind andstabilize cellular microtubules, thus preventing the migration, mitosis,and hyperproliferation of vascular smooth muscle cells, fibroblasts, andcirculating immune cells.

Paclitaxel and other drugs for the treatment of vascular disease presentseveral issues when used for coating endovascular medical devices, andwhen used for local release from the coated endovascular medical deviceto a surrounding tissue. Paclitaxel is only sparingly soluble in wateror biological fluids such as blood, and it has a relatively narrowtherapeutic window. Thus, while paclitaxel-eluting endovascular medicaldevices are used for the treatment of vascular disease, they are notcompletely effective due to a lack of coating robustness and drugelution considerations.

For example, the drug must first of all, be eluted from the coatedendovascular medical device into the surrounding tissue during thecontact time, whether it be short-term or long-term contact. The eluteddrug must be transferred to the cells lining the diseased vessel, ratherthan be washed away by flowing blood. Finally, the drug must beavailable to the cells fora sufficient length of time, and at anappropriate concentration range, to exert its pharmacological effectswhile minimizing its side effects. Also, the drug coating must meetcertain manufacturing and clinical needs to be an effective andcommercially viable treatment for vascular disease. The polymorph formof paclitaxel, along with substrate characteristics, can influence thedegree of coating robustness and the drug elution characteristics.

Paclitaxel is known to exist as several crystalline polymorphs andsolvate or hydrate polymorphs (i.e., a crystal form with stoichiometricor non-stoichiometric amounts of solvent or water); the most studiedbeing an amorphous form, an anhydrous crystalline form, and a dihydratecrystalline form. All three polymorphs have found use as coatings onmedical devices for the local treatment of vascular disease. Thesepolymorphs have numerous physical shapes, known in the art as a habit,including needles, plates, columns, irregular particles, spheres, etc.The ability of paclitaxel to dissolve (i.e., enter dissolution) in anaqueous or biological fluid is dependent upon the polymorph and thehabit, as is its bioavailability and mechanical properties. Thepreparation and physical structure of various paclitaxel polymorphs havebeen previously described (for example, S H Pyo, Drying Technology, 25,1759, 2007; J W Yoon, Korean J Chem Eng, 28, 1918, 2011; U.S. Pat. No.6,858,644 to Benigni et al.).

Paclitaxel in its amorphous polymorph can be characterized by a lack ofcrystallinity, as measured by differential scanning calorimetry (DSC),X-ray diffraction (XRD), and other techniques known to the art.Amorphous paclitaxel can be prepared, inter alia, by solvent evaporationfrom solutions comprising low- or non-polar solvents such asdichloromethane (for example, Yoon, op. cit.; JH Lee, Bull Korean ChemSoc, 22, 925, 2001) The art describes amorphous paclitaxel typicallytaking the form of glasses, irregular fine particles, or grape-likeparticles. Amorphous paclitaxel is most soluble in organicpharmaceutical solvents and oils, such as polyglycols comprisingpoloxamer, for use as a liquid formulation.

Paclitaxel in its anhydrous crystalline polymorph is characterized by amelting temperature of about 223° C. as measured by DSC. Anhydrouscrystalline paclitaxel can be prepared, inter alia, by precipitationfrom an organic solvent such as acetone, into a miscible organicnonsolvent such as ethyl acetate. Anhydrous crystalline paclitaxelfurther can be prepared, inter alia, by recrystallization from a polarorganic solvent such as alcohol, acetone, or acetonitrile. Anhydrouscrystalline paclitaxel has a unique XRD spectrum and a unique FTIRspectrum.

Paclitaxel in its dihydrate crystalline polymorph is characterized by aloss of water upon heating to as measured by thermal gravimetricanalysis, and by various endothermic peaks at 70-140° C. as measured byDSC. Dihydrate crystalline paclitaxel can be prepared, inter alia, byprecipitation from an organic, water miscible solvent such as acetone,into aqueous nonsolvent such as water. Dihydrate crystalline paclitaxelhas a unique XRD spectrum and a unique FTIR spectrum, distinct from theanhydrous polymorph. The typical habit of dihydrate crystallinepaclitaxel is regular needle- (acicular) shaped aggregates and regularplate-shaped aggregates. Dihydrate crystalline paclitaxel typically hasthe least apparent solubility in aqueous media of the three polymorphs.

Several references briefly discussed below describe various uses ofpaclitaxel in combination with endovascular medical devices.

Paclitaxel has been coated into the microstructure of endovascularmedical devices, such as vascular grafts comprising porous ePTFE, usinga solvent evaporation process (B. H. Lee, “Paclitaxel-coated expandedpolytetrafluoroethylene haemodialysis graft inhibit neointimalhyperplasia in porcine model of graft stenosis,” Nephrol DialTransplant, 21, 2432, 2006). As described in the Lee reference,paclitaxel was loaded onto ePTFE vascular grafts using a dipping method.Briefly, dry paclitaxel was dissolved in acetone at 2 mg/ml or 10 mg/ml,and ePTFE vascular grafts were dipped vertically into these solutionsand incubated for 30 minutes at 37° C. The paclitaxel loaded ePTFEvascular grafts were then dried and maintained under vacuum overnight tocompletely remove the solvent. No teachings were given on a paclitaxelcrystal high aspect ratio habit adherent to the vascular graft, nor howto facilitate projection or extension of a paclitaxel crystal highaspect ratio habit from or into the ePTFE vascular graft. For example,see Example 12 infra and shown by FIG. 12A infra, wherein the acetonesolvent yielded a smooth, glassy coating in an example of the instantdisclosure.

U.S. Patent Publication No. 2010/0268321 to McDermott et al. teachesimplantable medical device having a porous polymer (e.g., ePTFE, etc.)and crystals formed inside the pores of the porous polymer. The crystalscan be paclitaxel. However, no teachings were given to a drug crystalhigh aspect ratio habit embedded within the porous polymer or themedical device, nor how to facilitate projection of a drug crystal highaspect ratio habit with respect to the substrate.

U.S. Pat. No. 6,827,737 to Hill et al. teaches an implantable compositedevice that is a multi-layered tubular structure which is particularlysuited for use as an endoprosthesis or vascular graft. The prosthesisincludes at least one extruded polytetrafluoroethylene (PTFE) tube.Furthermore, the prosthesis includes a second tube of a polymericmaterial designed to regulate delivery of a drug associated with theprosthesis to the site of implantation. The drug may be encapsulatedwithin the polymer. The drug can be paclitaxel. No teachings were givenon a drug crystal having a high aspect ratio habit projecting from aporous polymer or a medical device, nor extending at least partiallyinto a porous polymer or a medical device.

U.S. Patent Publication No. 2011/0015664 to Kangas et al. teaches adrug-eluting balloon wherein paclitaxel is coated in an amorphous formonto a balloon surface comprising the polymer Pebax®, and then theamorphous paclitaxel is converted to a desired crystalline form in anannealing step that grows the crystalline drug in the coating in-situ onthe balloon. Vapor annealing of a continuous integral amorphouspaclitaxel coating results in solid state (or semi-solid)crystallization of the drug leading to crystalline coatings with thecrystals oriented parallel to the balloon surface and robust crystalpacking. As a point of contrast, this reference also shows an image of across-section of a prior art balloon in a folded configuration thatshows small rod-like crystals in the fold area, but they show very poorassociation with the surface and seem to have grown to loosely fill voidspace under the balloon folds, with many crystals extending outwardfrom, rather than parallel to, the surface. No teachings were given on adrug crystal high aspect ratio habit that projects from a porouspolymer, nor a drug crystal high aspect ratio habit that extends into aporous polymer.

U.S. Patent Publication No. 2010/0272773 to Kangas et al. teaches aprocess for a medical device, an angioplasty balloon, having a drugcoating thereon, wherein the drug has a plurality of characteristicmorphological forms, wherein the process is controlled to produce apredetermined ratio of said morphological forms on the device. Thesample from 20/80 THF/EtOH shows well formed fan-like paclitaxelcrystals covering the balloon. The sample from 40/60 THF/EtOH showsdiscrete rod-like crystals. The annealing process is effective atconverting the DEB coating from amorphous paclitaxel to crystallineform. No teachings were given on a drug crystal high aspect ratio habitthat projects from a porous polymer, or a drug crystal high aspect ratiohabit that extends into a porous polymer.

Many endovascular treatments require a sufficient amount of adhesion ofthe drug particle to the device substrate to withstand manufacturing anddelivery, but also be readily detached from the device substrate uponcontact with the treatment site to the tissue surface. Thus, a drugcoating with improved robustness and adequate attachment to remainmostly intact during the handling and manipulations of manufacturing andduring the medical procedures but detached upon tissue contact would bebeneficial. In addition, such drug coatings that also reduce drugdegradation or epimerization would also be beneficial.

SUMMARY OF THE DISCLOSURE

The present disclosure is directed toward composite materials comprisinghigh aspect ratio habits of drug crystals which can be partially orfully extending into a substrate, and additionally, can be projectingfrom a substrate at an angle of about 20° to about 90°. The presentdisclosure is directed toward medical devices, such as medical balloons,comprising said composite. Said composite can be robust and provideimproved attachment during manufacturing and during use of the device.The described composite can be used for the local treatment of vasculardisease. The present disclosure is also directed toward paclitaxelcrystals with a hollow acicular habit.

In accordance with one aspect of the disclosure, a composite materialcan comprise a plurality of high aspect ratio paclitaxel crystalsextending at least partially into said porous substrate and optionallyprojecting from a porous substrate at an angle of at least 20 to 90degrees relative to the substrate. In various embodiments, the substrateis a polymeric substrate. In various embodiments, the substratecomprises a porous microstructure, which can optionally compriseinterconnected fibrils or nodes interconnected by fibrils. In variousembodiments, at least a few of the plurality of paclitaxel crystals candefine a lumen extending along the length of a paclitaxel crystal. Invarious embodiments, the few of the plurality of paclitaxel crystals cancontain a second material located in the lumen. In various embodiments,the second material is at least one of less soluble or more soluble inan aqueous environment than the paclitaxel crystals. In variousembodiments, the lumen can be sealed. In various embodiments, theplurality of paclitaxel crystals can be acicular. In variousembodiments, the high aspect ratio crystals can have a ratio such that amajor dimension is at least four times the minor dimension. In variousembodiments, the substrate comprises a plurality of discrete crystals.In various embodiments, the substrate comprises a plurality of crystalaggregates. In various embodiments, the substrate comprises ePTFE. Invarious embodiments, the ePTFE can be coated with at least one of PVA,PEI, and PVP. In various embodiments, the substrate can be modified byat least one of plasma treatment, corona treatment, and surfactanttreatment. In various embodiments, a majority of the plurality ofpaclitaxel high aspect ratio crystals comprise a flat tip. In variousembodiments, a majority of the plurality of paclitaxel high aspect ratiocrystals comprise a jagged tip.

In accordance with another aspect of the disclosure, a method ofpreparing a composite comprising a porous substrate and a drug crystalof high aspect ratio habit, such that the crystals are at leastpartially extending into the substrate and are projected from substrateat an angle of about 20 to 90 degrees with respect to the substrate andcomprising the steps of preparing a solution of drug in the organicsolvent, wherein the organic solvent is capable of wetting thesubstrate; applying the solution to the porous substrate; and causingthe solvent to evaporate to form the drug crystal. In variousembodiments, the substrate can comprise a node and fibril microstructureor microstructure of interconnected fibrils. In various embodiments, thesubstrate can comprise ePTFE. In various embodiments, the drug cancomprise paclitaxel. In various embodiments, the drug crystal can be ahollow, acicular crystal. In various embodiments, the organic solventcomprises methanol. In various embodiments, the method can furthercomprise the step of treating the composite with at least one of solventannealing, vapor annealing, and thermal annealing. In variousembodiments, applying the solution can comprise at least one ofpipetting, dipping and spraying. In various embodiments, the method canfurther comprise the step of applying a non-solvent, wherein thenon-solvent comprises at least one of water, and ethyl acetate. Invarious embodiments, the porous substrate can form a surface of amedical device. In various embodiments, the medical device can be acatheter-based device.

In accordance with another aspect of the disclosure, a method oftreating a disease locally can comprise the steps of radially expandingmedical device from a first diameter to a second diameter, wherein themedical device comprises a substrate and the substrate contacts a tissueupon expansion, wherein the substrate comprises a polymeric substratecomprising a plurality of high aspect ratio paclitaxel crystals that atleast partially extend into the substrate and can at least partiallyproject from the substrate at an angle of at least 20 to 90 degreesrelative to the substrate. In various embodiments, the substrate cancomprise an excipient located thereon or within. In various embodiments,at least a portion of the plurality of high aspect ratio paclitaxelcrystal can penetrate the tissue.

In accordance with another aspect of the disclosure, a drug crystal cancomprise paclitaxel having a hollow crystal habit. In variousembodiments, the hollow crystal habit is acicular. In variousembodiments, the hollow crystal habit can be at least partially filledwith another material. In various embodiments, the drug crystal islocated on the surface of a medical device.

In accordance with another aspect of the disclosure, a compositematerial can comprise a substrate comprising a porous microstructure andan amount of crystalline paclitaxel comprising hollow crystal habitsassociated with the substrate. In various embodiments, the hollowcrystal habits can be acicular. In various embodiments, the few of theplurality of paclitaxel crystals can contain a second material locatedin the lumen. In various embodiments, the second material is at leastone of less soluble or more soluble in an aqueous environment than thepaclitaxel crystals. In various embodiments, the lumen can be sealed. Invarious embodiments, the substrate can be polymeric. In variousembodiments, the porous microstructure comprises interconnected fibrilsor nodes interconnected by fibrils. In various embodiments, thesubstrate can be expanded polytetrafluoroethylene.

In accordance with another aspect of the disclosure, a method of makinga drug delivery device having a substrate can comprise applying asolution comprising paclitaxel and an organic solvent to the substrate;allowing paclitaxel to crystallize through evaporation of the solvent,wherein the substrate comprises a polymer having a node and fibrilmicrostructure or a microstructure of interconnected fibrils and whereinthe organic solvent is capable of wetting the microstructure. In variousembodiments, the polymer can comprise ePTFE. In various embodiments, theorganic solvent can comprise at least one of methanol and ethanol.

In accordance with another aspect of the disclosure, a method of makinga drug delivery device having a substrate can comprise the steps ofapplying a solution comprising paclitaxel to a substrate; causing thepaclitaxel to crystallize; and exposing the paclitaxel to a vapor phasesolvent to cause the paclitaxel to form acicular crystal habits thatproject from the surface at an angle of between 20 to 90 degrees. Invarious embodiments, the vapor phase solvent can comprise at least oneof acetonitrile, methanol, and ethanol.

In accordance with another aspect of the disclosure, a medical devicecomprising an outer surface having a porous substrate and a plurality ofhigh aspect ratio drug crystals, such as paclitaxel crystals, extendingat least partially into said porous substrate, wherein the medicaldevice comprises a first diameter and a second, diameter and thesubstrate is adapted to contact a tissue upon expansion to the seconddiameter. In various embodiments, the plurality of high aspect ratiocrystals can project from the porous substrate at an angle of at least20 to 90 degrees relative to the substrate. In various embodiments, atthe first diameter, at least a portion of the plurality of high aspectratio crystals do not project beyond to substrate, and optionally, atthe second diameter, at least a portion of the plurality of high aspectratio crystals can project from the porous substrate at an angle of atleast 20 to 90 degrees relative to the substrate. In variousembodiments, the porous substrate has a first thickness at a firstdiameter and a second thickness at a second diameter, wherein the firstthickness is greater than the second thickness. In various embodiments,the medical device comprises an angioplasty balloon. In variousembodiments, the porous substrate can comprise interconnected fibrils ornodes interconnected by fibrils. In various embodiments, the poroussubstrate can comprise an expanded fluoropolymer. In variousembodiments, the porous substrate can comprise expandedpolytetrafluoroethylene. In various embodiments, the expandedpolytetrafluoroethylene has been plasma treated to create densifiedregions on the outermost surface.

BRIEF DESCRIPTION OF THE DRAWINGS

The features and advantages of the present disclosure will become moreapparent from the detailed description set forth below when taken inconjunction with the drawings, wherein:

FIG. 1 is a schematic of a balloon device having a porous substrate onits outer surface and an SEM micrograph showing crystalline paclitaxelaggregates coated from methanol solvent onto the porous substratecomprising ePTFE of a microstructure comprising very highly elongatednodes interconnected by fibrils.

FIG. 2 is a schematic illustration of the angle of projection of acrystal relative to a substrate.

FIG. 3A is an SEM micrograph showing discrete hollow acicular paclitaxelcrystals coated from methanol onto a porous substrate comprising ePTFEof a microstructure comprising very highly elongated fibrils.

FIG. 3B is an SEM micrograph at a higher magnification showing discretehollow acicular paclitaxel crystals coated from methanol onto a poroussubstrate comprising ePTFE of a first microstructure comprising veryhighly elongated fibrils.

FIG. 4 is an SEM micrograph showing acicular paclitaxel crystalaggregates comprising a urea excipient coated onto a porous substratecomprising ePTFE of a first microstructure comprising very highlyelongated fibrils.

FIG. 5 is a scanning electron microscope (SEM) micrograph showingpaclitaxel coated from acetonitrile solvent onto a nonporous substratecomprising nylon.

FIG. 6 is an SEM micrograph showing crystalline paclitaxel aggregatescoated from methanol solvent onto a nonporous substrate comprisingnylon.

FIG. 7 is an SEM micrograph showing crystalline paclitaxel aggregatescomprising a urea excipient coated onto a nonporous substrate comprisingnylon.

FIG. 8 is an SEM micrograph showing paclitaxel coated from acetonitrilesolvent onto a porous substrate comprising ePTFE of a microstructurecomprising very highly elongated fibrils.

FIG. 9 is an SEM micrograph showing crystalline paclitaxel aggregatescomprising a urea excipient coated onto a porous substrate comprisingePTFE of a microstructure comprising very highly elongated nodesinterconnected by fibrils.

FIG. 10 is an SEM micrograph showing paclitaxel crystals engaged andembedded into a vascular tissue.

FIGS. 11A to 11D are SEM micrographs showing paclitaxel crystals ofvarious habits coated from methanol solvent and various vapor annealing,onto a porous substrate comprising ePTFE of a microstructure comprisingvery highly elongated fibrils.

FIGS. 12A to 12D are SEM micrographs showing paclitaxel crystals ofvarious habits coated from acetone solvent and various vapor annealing,onto a porous substrate comprising ePTFE of a microstructure comprisingvery highly elongated fibrils.

FIGS. 13A to 13D are SEM micrographs showing paclitaxel crystals ofvarious habits comprising a urea excipient coated from methanol solventand various vapor annealing, onto a porous substrate comprising ePTFE ofa microstructure comprising very highly elongated fibrils.

FIGS. 14A to 14D are SEM micrographs showing paclitaxel crystals ofvarious habits coated from methanol solvent and various vapor annealing,onto a porous substrate comprising ePTFE of microstructure comprisingvery highly elongated nodes interconnected by fibrils.

FIGS. 15A to 15D are SEM micrographs showing paclitaxel crystals ofvarious habits coated from acetone solvent and various vapor annealing,onto a porous substrate comprising ePTFE of microstructure comprisingvery highly elongated nodes interconnected by fibrils.

FIGS. 16A to 16D are SEM micrographs showing paclitaxel crystals ofvarious habits comprising a urea excipient coated from methanol solventand various vapor annealing, onto a porous substrate comprising ePTFE ofmicrostructure comprising very highly elongated nodes interconnected byfibrils.

FIGS. 17A to 17B are SEM micrographs showing paclitaxel crystals ofvarious habits coated from acetonitrile solvent and various vaporannealing, onto a porous substrate comprising ePTFE of microstructurecomprising very highly elongated nodes interconnected by fibrils.

FIGS. 18A to 18B are SEM micrographs showing paclitaxel crystals ofvarious habits coated from chloroform solvent and various vaporannealing, onto a porous substrate comprising ePTFE of microstructurecomprising very highly elongated nodes interconnected by fibrils.

FIGS. 19A to 19D are schematics of a porous substrate comprisingembedded drug crystals, wherein the porous substrate is compressible inits thickness dimension, and the embedded crystals are not compressiblealong their axes dimension, and wherein upon compression of the poroussubstrate in its thickness dimension the drug crystals project from theporous substrate.

FIGS. 20A and 20B show SEM micrographs of a porous ePTFE microstructurecomprising islands of PTFE or densified regions of ePTFE attached to andatop an underlying ePTFE microstructure, in cross section view and inplan view.

FIGS. 21A to 21C are schematics of a porous ePTFE substrate.

FIG. 22 is a SEM micrograph showing discrete hollow acicular paclitaxelcrystals coated from methanol onto a porous substrate comprising ePTFEof a microstructure comprising very highly elongated fibrils, afterethylene oxide sterilization.

FIG. 23 is a SEM micrograph showing discrete hollow acicular paclitaxelcrystals coated onto a porous substrate comprising ePTFE of amicrostructure comprising very highly elongated fibrils, after ethyleneoxide sterilization.

FIG. 24 is an SEM micrograph showing paclitaxel coated from methanolonto a porous substrate comprising ePTFE of a microstructure comprisingislands of PTFE or densified sections of ePTFE attached to and atop anunderlying ePTFE microstructure, wherein the crystals occupy theunderlying ePTFE microstructure.

FIG. 25 is an SEM micrograph showing paclitaxel comprising a ureaexcipient coated from methanol onto a porous substrate comprising ePTFEof a microstructure comprising islands of PTFE or densified sections ofePTFE attached to and atop an underlying ePTFE microstructure, whereinthe crystals occupy the underlying ePTFE microstructure.

DETAILED DESCRIPTION OF THE DISCLOSURE

Persons skilled in the art will readily appreciate that various aspectsof the present disclosure can be realized by any number of methods andapparatuses configured to form he intended functions. Stateddifferently, other methods and apparatuses can be incorporated herein toperform the intended functions. It should also be noted that theaccompanying drawing figures referred to herein are not all drawn toscale, but may be exaggerated to illustrate various aspects of thepresent disclosure, and in that regard, the drawing figures should notbe construed as limiting. Finally, although the present disclosure maybe described in connection with various principles and beliefs, thepresent disclosure should not be bound by theory.

The disclosure relates to composites comprising substrates comprisingdrug crystals of high aspect ratio habit which project from a substrateand extend (embed?) at least partially into the porous substrate, aswell as their methods of preparation and their methods of use, e.g., inthe treatment of vascular disease. The present disclosure furthermorerelates to methods of treating or preventing a vascular disease with acomposite comprising a porous substrate and drug crystals of high aspectratio habit projecting from the porous substrate, as well as theirmethods of preparation and their methods of use in the treatment ofvascular disease. Said high aspect ratio crystals can be paclitaxel,which can be in solid or hollow form. Lastly, the disclosure is alsodirected toward hollow, acicular habits of paclitaxel, as well as themethods of use and preparations thereof.

A “habit” of a crystal describes its visible external shape. It canapply to an individual, discrete crystal, or to an aggregate ofcrystals. It can apply to a crystal visualized by any of a number ofmeans, including but not limited to the naked eye, optical microscopy,electron microscopy, and nanoindentation.

A “high aspect ratio” habit is a crystal habit that has a majordimension length and a minor dimension length, such that the majordimension length is about at least four (4) times longer than the minordimension length.

A “polymorph” is a material's molecular crystalline structure existingas two or more forms. Polymorphs can be the result of hydration,solvation, and unique molecular packing. The different forms of amaterial's amorphous molecular structure (i.e., there is no long-rangeordering of the molecules) can also be considered a polymorph.

“Acicular” is a habit characterized by an elongated, slender,needle-like or column-like structure. It can apply to an individual,discrete crystal, or to an aggregate of crystals. An acicular crystalhas a high aspect ratio. An acicular crystal can be solid or hollow.When referred to as hollow, an acicular crystal habit has a lumen thatextends longitudinally into at least a portion of the crystal.

A “therapeutic agent” as used herein, which is used interchangeably withthe term “drug”, is an agent that induces a therapeutic or bioactiveresponse in a cell, a tissue, an organ, or an organism including mammalsor that aids in detection or some other a diagnostic procedure.

The term “medical device” includes, but is not limited to, a medicalballoon (e.g., an angioplasty balloon), a stent, a stent graft, a graft,heart valve, heart valve frame or pre-stent, occluder, sensor, marker,closure device, filter, embolic protection device, anchor, cardiac orneurostimulation lead, gastrointestinal sleeves, and the like.

The term “vascular disease” includes, but is not limited to, vascularinjury, vascular trauma, vascular prophylactic intervention, intimalhyperplasia, phlebitis, vulnerable plaque, carotid plaque, coronaryplaque, peripheral plaque, vascular plaque, aneurismal disease, vasculardissection, atherosclerotic plaque, atherosclerotic lesion, vascularinfection, vascular inflammation, stenosis, restenosis, and vascularsepsis.

The term “adhesion” includes to stick or to engage with a surface, e.g.,the luminal wall of a vessel.

The terms “penetration”, “penetrating”, “penetrate”, and the like, are atype of adhesion wherein an object has entered into, passed through,embedded, or pierced the outermost plane of a surface of a substrateinto the interior of the substrate.

The terms “project”, “projecting”, “projection” and the like, are anorientation of an object where the object extends beyond the outermostplane of the substrate.

The terms “projection angle”, “angle of projection”, and the like, arethe geometric angle that a projecting object has relative to theoutermost plane of the substrate surface.

In accordance with one aspect of the present disclosure, with referenceto FIG. 1, a substrate 100 comprises a plurality of high aspect ratiocrystals 110 comprising a therapeutic agent and projecting from thesubstrate 100 and optionally, extending into the substrate. The highaspect ratio crystals 110 can comprise an acicular habit and optionallya hollow acicular habit. The angle of projection 101 (see FIG. 2)relative to the substrate 100 can range from about 20 to 90 degrees. Theplurality of crystals 110 can project from the substrate within thespecified angle along a substantial portion of the section of coatedsubstrate. Further, the plurality of crystals 110 can project from thesubstrate at an angle with respect to a flat section of substrate, i.e.,a section that is not creased, folded, or wrinkled. In a furtherembodiment, the substrate 100 can comprise a porous microstructure (asin FIGS. 19A and 20A), and optionally, at least some of the high aspectratio crystals 110 extend at least partially into the porousmicrostructure (as in FIG. 19B). The crystals 110 can be formed directlyon the substrate 100. The angle of projection can be estimated ormeasured using a number of techniques, including but not limited tovisualization using optical microscopy and SEM.

In forming directly on the substrate 100, the substrate 100 can compriseany suitable porous microstructure wherein the microstructurefacilitates crystal formation that projects from, and optionally, atleast partially extends into the substrate 100. In various embodiments,the porous microstructure comprises expanded fluoropolymer membranes.Non-limiting examples of expandable fluoropolymers include expandedPTFE, expanded modified PTFE, and expanded copolymers of PTFE. Patentshave been filed on expandable blends of PTFE, expandable modified PTFE,and expanded copolymers of PTFE, such as, for example, U.S. Pat. No.5,708,044 to Branca; U.S. Pat. No. 6,541,589 to Baillie; U.S. Pat. No.7,531,611 to Sabol et al.; U.S. patent application Ser. No. 11/906,877to Ford; and U.S. patent application Ser. No. 12/410,050 to Xu et al.The substrate 100 can also comprise a porous or fibrillated ultra-highmolecular weight polyethylene (UHMWPE), a porous electrospun materialand other porous polymers and metals.

The microstructure architecture can be varied to vary crystalproperties, such as the habit type (e.g., clustered or discretecrystals, rod- or needle-like crystals, both solid and hollow), thedimensions (e.g., thickness, width, or aspect ratio), the geometry(e.g., hollow versus solid geometries), the orientation (e.g.,projecting from the substrate) relative to the substrate, and the purityand perfection of the crystal. The porous microstructure can comprisenodes and fibrils, the size and spatial qualities of which can bevaried. For example, in some embodiments, the microstructure can behighly fibrillated or have no distinguishable or very small nodes. Inother embodiments, the microstructure can have large or elongated nodes.In yet other embodiments, the microstructure can have a node and fibrilmicrostructure somewhere in between, e.g., a microstructure withintermediate-sized nodes. Additionally, the porosity or average poresize of the microstructure can create a tight microstructure or an openmicrostructure. “Tight” as used herein means that the spacing betweenthe fibrils, nodes, or fibrils and nodes is smaller than the width ofthe exposed section of crystal. For example, in FIG. 13C, the crystals110 are shown, and the width of the crystals 110 is much larger than themicrostructure 100 on which they were formed. “Open” as used hereinmeans that the spacing between the fibrils, nodes, or fibrils and nodesis larger than or equal to the width of a crystal. For example, in FIG.1, the crystals 110 are shown passing through the spacing of the fibrils105. Both microstructures allow for extension and/or embedding into themicrostructure. Other porous microstructures that facilitate projectionsfrom, and optionally, at least partial extension and/or embedding of thecrystal into the substrate, includes woven, knitted, felted, carded,spun, laser drilled, and/or neutron drilled materials or the like. Saidporous microstructure can be further treated or coated to vary crystalformation, such as by plasma, corona, and/or surfactant treatment orcoated with polyvinyl alcohol (PVA), polyethyleneimine (PEI),polyvinylpyrollidone (PVP), or other polymeric coatings. Said treatmentsand coatings may modify the surface energy of the substrate, or maymodify the microstructure of the substrate. For example, the substratemay be modified for example by a combination of high energy processingfollowed by heating, to produce inter alia three dimensionalmicrostructures on the substrate surface, such as those described inU.S. Pat. No. 7,736,739.

Similarly, the concentration levels of the therapeutic agent and/orsolvent or blend of solvents (referred herein as a solvent system) fromwhich the crystals form can be adjusted to adjust the habit (e.g.,clustered or discrete crystals, rod- or needle-like crystals), thedimensions (e.g., thickness, width, or aspect ratio), the geometry(e.g., hollow versus solid geometries), the orientation relative to thesubstrate, and the purity and perfection of the crystal. The solventsystem can comprise an organic solvent(s) and/or supercritical solvents,wherein the solvent has the ability to wet the substrate and has theability to dissolve the therapeutic solvent. Optionally, the microporoussubstrate may be surface-treated to aid the wetting and imbibement ofsolvent containing dissolved therapeutic agent, or to aid the formationof crystals during crystallization.

For crystals grown by solvent evaporation under ambient conditions(about 25° C. and about 1 atm barometric pressure), the solvent systemhas a volatility and heat capacity to readily evaporate and inducesuper-saturation of the therapeutic agent. For example, a solvent systemfor solvent evaporation crystallization techniques can comprise methanoland/or ethanol. Methanol and/or ethanol as a primary solvent facilitatehollow acicular crystals under certain conditions. The solutionconcentration can be on the order of about 0.001 mg/ml to about 100mg/ml.

A solvent system can comprise a solvent system additive(s) which canalter the dimension, habit, tip feature, and the like. For example, asolvent system can comprise methanol and urea. The ratio of thetherapeutic agent to urea can range from 10:1 to 1:15 or more.

Also relevant to affecting the crystal properties is the manner ofcrystallization. High aspect ratio habits of crystals can be fully orpartially adhered onto or into a porous substrate, such as ePTFE, usinga variety of coating methods, including but not limited to solventevaporation and vapor annealing. A method of crystallization cancomprise at least one of solvent evaporation or vapor annealing. Using asolvent evaporation method, the drug is dissolved in an appropriatesolvent and applied to the substrate, whereupon during and afterevaporation of the solvent the drug crystallizes as a high aspect ratiohabit that is fully or partially embedded, adhered, or otherwise coatedonto the ePTFE. The solvent can be applied to the substrate with avariety of techniques including pipetting, dipping, spraying, brushing,and the like.

Using vapor annealing method, the drug is dissolved in an appropriatesolvent, applied to the substrate, and the solvent evaporated, whereuponexposure to an appropriate solvent vapor the drug crystallizes as a highaspect ratio habit that is fully or partially embedded, adhered, orotherwise coated onto the porous ePTFE. Solvent systems for vaporannealing can comprise at least one of acetonitrile, methanol,tetrahydrofuran, chloroform, isopropyl alcohol, hexane, and ethanol.

Other techniques or post-crystallization treatments can include thermalannealing, quenching, vitrifying, vacuum, sonicating, and/or. Saidtechniques can be utilized to alter the habit type, dimensions,orientation, perfection, or purity. On the other hand,post-crystallization techniques can preserve or inconsequentially alterthe habit type, dimension, orientation, perfection, and/or purity. Forexample, as described in Example 9, sterilizing the substrate withethylene oxide did not consequentially impact the crystal properties.

Crystal geometry, dimension, uniformity, perfection, or purity canfacilitate adhesion and, optionally, penetration into a tissue. Thesefactors can be controlled by varying the concentration of the solution,the type of substrate, the architecture of the substrate'smicrostructure, the type of solvent(s), the crystallization technique orprocessing, and the like. For example, the aspect ratio of a crystal canbe adjusted to be 1:4 up to 1:50 or more. The shape of the end of thecrystal can also be adjusted. For example, the tip 111 can be agenerally flat tip (as shown, e.g., in FIGS. 1, 3A and 4 and FIGS. 11Ato 11C) or a more pointed or jagged tip 111 (as shown, e.g., in FIGS.14A, 14C, 14D, and 15C). These cited images are only provided asillustrative samples and are not the only images of flat, jagged, orpointed ends provided herein. Another variation includes coating asubstrate with a plurality of discrete crystals 110 (as shown in FIG.3A) or a plurality of crystal aggregates or clusters 112 (as shown inFIG. 11A).

In accordance with the present disclosure, with reference again to FIG.1, a medical device 120 can comprise the high aspect ratio crystals 110as described located on the surface 100 of a medical device andprojecting from the surface 100. The medical device 120 can facilitateshort-term contact with a tissue or long-term to permanent contact witha tissue. Contact less than 10 minutes is short-term contact and contactgreater than 10 minutes is long-term contact. Said crystals 110 cancomprise or consist of paclitaxel. Said crystals 110 can have anacicular habit and further a hollow acicular habit.

The crystals 110 can be pre-coated to a medical device 120 such as avascular prosthesis, or a catheter-based device, such as a stent, stentgraft, or balloon, prior to catheter insertion into a vascularstructure. For example, the high aspect ratio crystals 110 can be coatedto at least one portion or one surface of a medical device, vascularprosthesis, or catheter-based device including, but not limited to, astent, stent graft, vascular graft, angioplasty balloon, microneedlestudded balloon, and other vascular prosthesis. The coating can becontinuous or discontinuous, covering at least a portion of the medicaldevice. Furthermore, the crystals 110 of the coating can be partially orfully adhered onto (and optionally, extend or embed into) at least onesurface of the medical device. In further embodiments, the crystals 110of the coating can project from said at least one surface at aprojection angle of about 20° to about 90°.

In another embodiment, the crystals are embedded in the microporoussubstrate and do not project from said at least one surface, as shown inFIGS. 19C and 20B. The crystals can be coated into the microporoussubstrate using techniques that prevent the projection of the crystalsbeyond the substrate outer surface. Alternatively, those portions of thecrystals that project beyond said substrate outer surface (such as seenin FIG. 19B) may be planed off, using apparati known to the artincluding but not limited to planing knives, laser ablation, electricalcurrent exposure, vapor exposure, solvent exposure, thermal exposure,mechanical abrasion, high energy processing such as plasma or corona,and the like. In this embodiment, the crystals that do not projectbeyond said substrate outer surface are effectively shielded againstdamage during manufacturing, storage, delivery to an anatomical site andinitial device deployment. In a further embodiment, said effectivelyshielded crystals are capable during device implantation of projectingbeyond the outer surface of said microporous substrate by causingcompression along the thickness of the substrate. In this manner, thecrystals can project from said outer surface at a projection angle ofabout 20° to about 90°, as shown in FIGS. 19D and 20C.

The coating on the medical device 120 comprising high aspect ratio habitcrystals 110 that are not parallel to the surface 100 can facilitate amore robust adhesion to the substrate useful during manufacturing andduring clinical procedures, as well as facilitate adhesion on oroptionally penetration into a tissue or into the wall of a tissue. Saidadhesion and optional penetration of individual particles of high aspectratio habit crystals 110 can facilitate an improved transfer and/orretention of crystals 110 from the medical device 120 to the tissue atthe site of contact, rather than be flushed from the site by flowingblood or other surgical techniques. The ability to create a particlecoating with projecting crystals 110 can facilitate an improved deliveryin terms of accuracy and reliability of dosing of the tissue duringcontact.

In accordance with the present disclosure, the high surface area, highvapor transmission rate, and relatively high thermal conductivity ofePTFE can facilitate drug solvation and mass transport, and provide fora steep thermal gradient, necessary for the growth of high aspect ratiohabit crystals that are fully or partially extending into themicrostructure. As is set forth in Example 8, such crystals show DSCthermal behaviors distinct from crystals that are adherent to, but thatdo not penetrate a non-porous substrate, including crystal melting andcrystal perfection.

In accordance with the present disclosure, a therapeutic agent that iscrystallized to form a high aspect ratio crystal on a porous substrateor extend at least partially into a substrate as described herein cancomprise paclitaxel and its analogs. Other suitable therapeutic agentsinclude rapamycin and its analogs. The therapeutic agents which can beused in embodiments of the present disclosure can be any therapeuticagent or substance that forms an acicular habit on a porous substrate orextends at least partially into a substrate.

The described therapeutic agent coated on the described substrate isdiscontinuous on a microscopic scale, even though it can appearcontinuous on a visual scale. The crystals being at least partiallyextended into the microstructure are not continuous, as thenodes/fibrils break up the coating's continuity, as illustratedschematically in FIGS. 19B, 19C and 20B. Thus, during a sufficientlyforceful contact with a tissue (e.g., a desired pressure of an inflateddevice in pressure contact with a tissue), the crystals can penetrateinto the tissue as smaller, more uniform particle sizes, as isillustrated in FIG. 10, rather than as disperse, large, continuoussheets (shards, flakes, etc) of drug coating. The size of the particlescan be controlled in the coating process to give a predictable sizedistribution during contact with the tissue.

In accordance with the present disclosure, the described substrates canbe utilized in interventional techniques. Interventional techniquesroutinely involve minimally invasive procedures. Often this technique isinitiated by a puncture or cut-down of a vascular structure andinsertion of a catheter through an interventional access site into thevascular structure. Interventional access sites can include, but are notlimited to, access through an implanted vascular prosthesis, brachialartery, carotid artery, iliac artery, femoral artery, aorta, and otherarterial or venous sites.

After insertion of a catheter through an interventional access site intothe vascular structure, the catheter can then be guided to a site with avascular disease in need of vascular treatment (i.e., a vasculartreatment site), from the interventional access site. The vasculartreatment site can include, but is not limited to, vascular conduitssuch as a blood vessel, a vascular graft, a vascular stent, a vascularfilter, a vascular anastomosis, and a vascular stent graft. In aninterventional treatment, a medical device contacts a treatment site.Following a contact time sufficient for at least a portion of the highaspect ratio habit crystals of drug to adhere to a vascular treatmentsite to treat the vascular disease, the medical device can be optionallyremoved. The contact time can be short term, can be long term, or can bepermanent.

By way of example, the high aspect ratio habit crystals of drugdescribed herein can be pre-applied to or formed on at least one surfaceof a catheter-based device prior to catheter insertion into a vascularstructure. For example, high aspect ratio habit crystals of drug can becoated to at least one surface of a catheter-based device including, butnot limited to, a stent, stent graft, medical balloon (e.g., aangioplasty balloon or microneedle studded balloon), and other vascularprostheses. The coating can be continuous or discontinuous, covering atleast a portion of the catheter-based device. The crystals of thecoating are fully or partially adhered onto and optionally extendedand/or embedded into at least one surface of the catheter-based device,as shown in FIG. 19B. In addition, said acicular crystals projectagainst said at least one surface at a projection angle of about 20° toabout 90°.

Catheter-based devices often have a first diameter and a first surfacearea prior to and during insertion of the catheter-based devices into avascular tissue. After insertion into the vascular tissue, thecatheter-based devices are mechanically expanded to a second diameterand a second surface area within the vascular structure. When thecatheter-based medical device is mechanically expanded to the seconddiameter and second surface area, the projecting crystals on the atleast one surface of the medical device adhere to the wall of thevascular tissue and optionally extend a portion of the crystals into thewall of the vascular tissue. The catheter-based medical device isoptionally returned to the first diameter and first surface areas,thereby allowing its removal from the vascular tissue. The saidprojecting crystals that have adhered onto and optionally penetratedinto the wall of the vascular tissue remain adhered onto and optionallypenetrated into the wall of the vascular tissue during the return of thecatheter-based medical device to the first diameter and first surfacearea, thereby treating the vascular disease.

In another embodiment of a catheter-based device having a first diameterand a first surface area prior to and during insertion of thecatheter-based devices into a vascular tissue, the crystals do notproject beyond the external surface of the device, as shown in FIGS. 19Cand 20B. In this manner, the crystals are embedded within themicroporous substrate, and are effectively encapsulated and mechanicallyprotected from damage during manufacturing or storage, and frompremature tissue exposure or particulation during device insertion intoa vascular tissue and tracking to the target tissue. After insertioninto the vascular tissue, the catheter-based devices are mechanicallyexpanded to a second diameter and a second surface area within thevascular structure. When the catheter-based medical device ismechanically expanded to the second diameter and second surface area,the embedded crystals then project beyond the outer surface of thesubstrate at a projection angle of 20-90°, as shown in FIGS. 19D and20C. The projecting crystals adhere to the wall of the vascular tissueand optionally penetrate a portion of the crystals into the wall of thevascular tissue. The catheter-based medical device is optionallyreturned to the first diameter and first surface areas, thereby allowingits removal from the vascular tissue. The said projecting crystals thathave adhered onto and optionally penetrated into the wall of thevascular tissue remain adhered onto and optionally penetrated into thewall of the vascular tissue during the withdrawal of the catheter-basedmedical device from the vascular tissue. In various embodiments, whenthe catheter-based medical device is mechanically expanded to the seconddiameter and second surface area, a substrate can comprise nodes,fibrils, or nodes and fibrils. In a further embodiment, these nodes,fibrils, or nodes and fibrils can undergo a change in alignment duringexpansion to the second surface area thereby altering the orientation ofthe said embedded crystals. This can facilitate rotation of, extensionof, or reorientation of the crystals so that they project beyond theouter surface of the substrate at a projection angle of 20-90°, as shownin FIGS. 19D and 20C.

Described composites can be utilized in surgical or interventionalprocedures, such as in catheter based vascular or non-vascular devices.In addition to vascular applications, the described composite can beused in relation to, gastrointestinal, neural, cranial, ophthalmic,orthopedic, renal, hepatic, urinary, sinus treatments, and the like.

In accordance with another aspect of the present disclosure, withreference to FIGS. 3A and 3B, the high aspect ratio habit crystals 110can comprise hollow acicular paclitaxel, which can be used in a clinicaltreatment or formulation, such as for the treatment of cancer orvascular disease. Such treatments or formulations include the additionof the crystals to an oral form, a tablet form, a suspension, anemulsion, a parenteral form, an intravenous form, an enteral form, aninjectable form, or other formulations. Such formulations may or may notinclude the need fora medical device. Such formulation may or may notinclude the addition of pharmaceutical vehicles, excipients, fillers,additives, nano- and micro-carriers, and the like. Such crystals can beremoved from the substrate upon which it was formed for use in thedescribed treatments and formulations.

In an embodiment, the lumen of the hollow crystals can be filled atleast partially with a second material, such as a therapeutic agent, anexcipient, an additive or a therapeutic agent and an excipient oradditive. The therapeutic agent can have an equal degree of aqueoussolubility than the paclitaxel hollow crystal or a greater or lesseramount of relative aqueous solubility. In addition, an end cap or sealof various materials can be placed on the tip of the hollow acicularcrystal once filled.

The following examples describe the manner, process of making, and usingthe present disclosure and are intended to be illustrative rather thanlimiting.

EXAMPLES Example 1

This example describes the preparation of a porous sample substratecomprising ePTFE of a first microstructure comprising very highlyelongated fibrils.

An ePTFE membrane of approximately 0.0002″ thickness was prepared as perU.S. Pat. No. 7,306,729 to Bacino et al., incorporated herein byreference in its entirety. A fluoropolymer adhesive comprising athermoplastic copolymer of tetrafluoroethylene and perfluoromethyl vinylether was prepared generally in accordance with U.S. Pat. Nos. 7,049,380and 7,462,675 to Chang et al., incorporated herein by reference in theirentirety. The ePTFE membrane was cut to approximately 20 mm×50 mm, andwas adhered to a glass slide (#48300-025, VWR). An adhesive solution wasprepared by dissolving the fluoropolymer adhesive in solvent (FluorinertFC-75, 3M) at a concentration of approximately 3%. A light coating ofthe adhesive solution was applied to the glass slide, and the ePTFEmembrane was applied and smoothed to remove wrinkles and bubbles, thenheated under slight pressure (approx 0.02 atm) at 60° C. in an oven for24 hr to remove the solvent.

Example 2

This example describes the preparation of a porous sample substratecomprising ePTFE of a second microstructure comprising very highlyelongated nodes interconnected by fibrils.

An ePTFE membrane of approximately 0.0007″ thickness was preparedgenerally in accordance with U.S. Pat. No. 5,814,405 to Branca et al.,incorporated herein by reference in its entirety. The ePTFE membrane wascut to approximately 20 mm×50 mm, and was adhered to a glass slide(#48300-025, VWR) as per Example 1.

Example 3

This example describes the preparation of a nonporous sample substratecomprising nylon.

A nylon balloon (part number BMT-035, Bavaria Medizin Technologie,Munich Germany) was inflated with air to remove folds and pleats. A20×50 mm film was cut from the balloon with a razor blade, and taped toa glass slide (#48300-025, VWR) using cellophane tape. The non-porousnature of this substrate is depicted in FIG. 5.

Example 4

This example describes the general procedure for the preparation of drugcrystals onto a substrate using solvent evaporation.

Paclitaxel (LC Laboratories, Boston Mass.) was dissolved at roomtemperature by stirring into methanol (ACS grade, Aldrich), acetonitrile(ACS grade, Aldrich), acetone (ACS grade, Aldrich), or chloroform(reagent grade, Sigma), at a concentration of 10 to 30 mg/ml, optionallycontaining urea (reagent grade, Sigma) at a mass ratio of 1:1 to 8:1(paclitaxel:urea). 50 to 500 μl of the paclitaxel solution was then castonto the substrates of Examples 1 through 3, by depositing the solutionfrom a pipettor over the surface area of the ePTFE or nylon substrates.The samples were air-dried in a laminar fume hood at about 20° C. at anambient atmospheric pressure of about 773 mm Hg to cause the solvent toevaporate. (The paclitaxel solution can be applied to the substrate in avariety of ways including pipetting, dipping, spraying, brushing, andthe like.)

Example 5

This example describes the SEM visualization and orientation of drugcrystals adhered onto the substrates of Example 3 as coated according toExample 4.

As seen in FIG. 5, paclitaxel 500 coated onto nylon 502 fromacetonitrile solvent (10 mg/ml) produced a smooth, continuous coating,absent of any high aspect ratio habits. As seen in FIG. 6, paclitaxelcoated onto nylon from methanol solvent (10 mg/ml) produced a pluralityof aggregates of paclitaxel crystals comprising high aspect ratiohabits. The aggregates were observed to be adherent to the nylonsubstrate, but did not penetrate or otherwise embed into the bulk of thenylon substrate. Most of the aggregates were observed to project fromthe nylon substrate at a projection angle of about 20° to about 90°relative to the substrate. As seen in FIG. 7, paclitaxel comprising aurea excipient (1:1 mass ratio) coated onto nylon from methanol (10mg/ml paclitaxel) produced a plurality of aggregates of paclitaxel/ureacrystals comprising multiple habits including irregular shapes,“coral”-like shapes, whiskers, rods, and the like. The aggregates wereobserved to be adherent to the nylon substrate, but did not extend intothe bulk of the nylon substrate. The aggregates did not show anyorientation relative to the nylon substrate.

Example 6

This Example describes the SEM visualization and orientation of drugcrystals embedded and oriented onto the substrates of Example 1 ascoated according to Example 4.

As seen in FIG. 8, paclitaxel coated from acetonitrile (10 mg/ml) ontoePTFE 840 of a first microstructure comprising very highly elongatedfibrils produced a smooth, continuous coating, absent of any high aspectratio habits. The paclitaxel coating 820 was cracked and separated,orienting and aligning the ePTFE fibrils, indicating the coating hadpenetrated and embedded into the bulk of the ePTFE substrate. As seen inFIG. 3A, paclitaxel coated from methanol (10 mg/m 1) onto ePTFE of afirst microstructure comprising very highly elongated fibrils produced aplurality of discrete, individual paclitaxel crystals comprising highaspect ratio habits. The discrete crystals were observed to penetrateand embed into the bulk of the ePTFE substrate, as indicated byelongated ePTFE nodes interconnected among the discrete crystals. Thediscrete crystals were observed to project from the ePTFE substrate at aprojection angle of about 20° to about 90° relative to the substrate.FIG. 3B is a higher magnification of FIG. 3A, showing the elongatedePTFE nodes interconnected among the discrete crystals, and showing thediscrete crystals projecting from the ePTFE substrate at a projectionangle of about 20° to about 90° relative to the substrate. As seen inFIG. 4, paclitaxel comprising a urea excipient (1:1 mass ratio) coatedfrom methanol (10 mg/ml paclitaxel) onto ePTFE of a first microstructurecomprising very highly elongated fibrils produced a plurality ofaggregates of paclitaxel/urea crystals comprising high aspect ratiohabits. The aggregates were observed to extend into the ePTFE substrate,as indicated by elongated ePTFE nodes interconnected among theaggregates. The aggregates were observed to orient relative to the ePTFEsubstrate at a projection angle of about 20° to about 90° with manyaggregates also laying parallel to the substrate surface.

Example 7

This example describes the SEM visualization and orientation of drugcrystals adhered and oriented onto the substrates of Example 2 as coatedaccording to Example 4.

As seen in FIG. 1, paclitaxel coated from methanol (10 mg/ml) onto ePTFEof a second microstructure comprising very highly elongated nodesinterconnected by fibrils produced a plurality of aggregates ofpaclitaxel crystals comprising high aspect ratio habits. The aggregateswere observed to extend into the bulk of the ePTFE substrate, asindicated by elongated ePTFE nodes interconnected throughout the crystalaggregates. The aggregates were observed to orient relative to the ePTFEsubstrate at a projection angle of about 20° to about 90°. As seen inFIG. 9, paclitaxel comprising urea excipient (1:1 mass ratio) coatedfrom methanol (10 mg/ml paclitaxel) onto ePTFE of a secondmicrostructure comprising very highly elongated nodes interconnected byfibrils produced a plurality of aggregates of paclitaxel/urea crystalscomprising multiple habits including high aspect ratio habits, columns,plates, irregular shapes, and the like. The aggregates were observed toextend into the bulk of the ePTFE substrate, as indicated by elongatedePTFE nodes interconnected throughout the crystal aggregates. Theaggregates were observed to orient relative to the ePTFE substrate at aprojection angle of about 20° to about 90°.

Example 8

This example describes the thermal behavior of high aspect ratio habitsof paclitaxel crystals as a function of the substrate.

Representative samples of Examples 5, 6, and 7, were examined undermodulated DSC (Model #Q2000, TA Instruments, New Castle, Del.), from−30° to 230° C., using a single heating ramp of 5° C./min, with anoscillation rate of +/−0.5° C. every 40 sec, under nitrogen. Standard Tzero pans were used.

Modulated-DSC is capable of discriminating between thermodynamic andkinetic contributions to a crystal's thermal properties during anoscillating heating ramp. The total heat flow is split into reversing(thermodynamic) and non-reversing (kinetic) heat flows. Thenon-reversing heat flow is those events that do not respond to theoscillating heating ramp, including transitions such as crystal melting,and the like related to crystal purity, recorded as a non-reversingendotherm is transition. The reversing heat flow derives from the heatcapacity of the sample; phenomena such as crystal polymorph phasede-organization/re-organization, atomic-scale group motion, crystalpolymorph phase reorganization, and the like related to crystalperfection, contribute to an excess heat capacity recorded as areversing exothermic transition. These transitions are reversible eventsthat respond to the oscillating heating ramp.

As seen in FIGS. 6, 1, and 3A, the paclitaxel crystals of each samplehave high aspect ratio habits with similar morphologies. Surprisingly,the thermal properties for each were unique and dependent upon thesubstrate.

For the sample prepared according to Example 5, the DSC thermogram wascomplex. There were various endothermic events at about 50° C. to about105° C., indicating loss of water. There was a non-reversing endothermat about 160° C., followed by a sharp non-reversing exotherm at about165° C., coincident with reversing excess heat capacity transitions atabout 165° C. and at about 170° C. There was a second non-reversingendotherm at about 175° C., again followed by reversing excess heatcapacity transitions at about 183° C. and at about 203° C. There was athird non-reversing endotherm at about 207° C.

For the sample prepared according to Example 6, the DSC thermogram wasless complex. There was a transition at about 19° C. (ePTFEtriclinic-hexagonal transition), followed by various endotherm is eventsat about 50° C. to about 105° C., indicating loss of water. There was anon-reversing endotherm at about 160° C. There was a broad non-reversingexotherm at about 170° C., followed by another non-reversing endothermat about 215° C.

For the sample prepared according to Example 7, the DSC thermogram wassimilar to that prepared according to Example 6. For the sample preparedaccording to Example 7, there was a transition at about 19° C. (ePTFEtriclinic-hexagonal transition), followed by various endothermic eventsat about 50° C. to about 105° C., indicating loss of water. There was anon-reversing endotherm at about 160° C. There was a broad non-reversingexotherm about 175° C., followed by another non-reversing endotherm atabout 215° C.

The major thermal events are summarized in Table 1.

TABLE 1 ePTFE second ePTFE first Temperature Nylon substratemicrostructure microstructure (approx ° C.) (Example 5) (Example 7)(Example 6)  19 — ePTFE ePTFE transition transition 50-105 Loss of waterLoss of water Loss of water (dihydrate) (dihydrate) (dihydrate) 160non-reversing non-reversing non-reversing endotherm endotherm endotherm165 non-reversing — — exotherm w/ reversing excess heat capacity 170reversing excess non-reversing — heat capacity exotherm 175non-reversing — non-reversing endotherm exotherm 183 reversing excess —— heat capacity 203 reversing excess — — heat capacity 207 non-reversing— — endotherm 215 — non-reversing non-reversing endotherm endotherm

As can be seen in Table 1, the DSC thermograms are distinct, even thoughthe high aspect ratio habits are similar in appearance. Comparing tonylon, the paclitaxel crystals on both ePTFE microstructures displayedshifts to higher temperatures in their non-reversing endotherms with anabsence of reversing excess heat capacity, suggesting that thesecrystals were more pure and more perfect, even though they share asimilar high aspect ratio habit. Furthermore, the high aspect ratiohabits of paclitaxel crystals prepared according to Example 6 showed thehighest non-reversing exotherm transition, suggesting the discrete,individual crystals, compared to aggregates of crystals, are mostperfect.

Without wishing to be bound by any particular theory, the inventorsbelieve the unique microstructure of porous, ePTFE substrates combinedwith the appropriate solvent and processing conditions, act as atemplate for the crystallization of drug preferentially as high aspectratio habits that extend into the porous ePTFE at a projection angle ofabout 20° to about 90°. The inventors believe ePTFE's high surface area,high vapor transmission rate, and relatively high thermal conductivity,provide means for drug solvation and mass transport, and means for asteep thermal gradient, necessary for the growth of high aspect ratiohabit crystals that are fully or partially embedded at a projectionangle of about 20° C. to about 90°.

This Example suggests that the substrate surprisingly and unexpectedlyaffects embedding of the high aspect ratio drug crystals in the bulk ofthe substrate, the orientation of crystals relative to the substrate,and the purity and perfection of the crystal structure.

Example 9

This Example describes the SEM visualization and orientation of drugcrystals embedded and oriented onto the substrates of Examples 1 and 2,as coated according to Example 4 after sterilization

Representative samples of Examples 6 and 7 were exposed to ethyleneoxide sterilization, under conditions of conditioning for about 24 hr,an EtO gas dwell time of about 22 hr, a set point temperature of 64° C.,and an aeration time of about 12 hrs. The samples were then visualizedwith SEM. The acicular habits of the paclitaxel crystals, theirgeometry, their penetration into the ePTFE microporous substrate, andtheir angles of projection, were unaffected by the ethylene oxidesterilization. For example, FIG. 22 is an SEM micrograph of the coatedsubstrate as seen in FIG. 3A after ethylene oxide sterilization. Foranother example, FIG. 23 is a SEM micrograph of the coated substrate asseen in FIG. 1 after ethylene oxide sterilization.

Example 10

This example describes the ex vivo transfer of drug crystals from anePTFE substrate to a vascular tissue.

Substrates of ePTFE of Examples 1 and 2 were coated with paclitaxel (10mg/ml) or paclitaxel/urea (1:1 mass ratio; 10 mg/ml paclitaxel)according to Example 4. The substrates were examined under SEM toconfirm the presence of high aspect paclitaxel crystal habits embeddedand oriented in the ePTFE microstructure.

A freshly harvested carotid artery from >2 yr old swine (AnimalTechnologies Inc., Tyler Tex.) was slit axially using a scalpel blade,cut lengthwise into portions, everted, and the portions adhered to aglass microscope slide using cyanoacrylate adhesive (Loctite), luminalaspect up. Tissue portions were kept wet using phosphate-buffered salineuntil use.

The glass microscope slide containing the artery portion was gentlyplaced, tissue side down, upon the coated ePTFE substrate, to expose theendothelial layer to the paclitaxel crystals. The endothelial layer wascompressed at about 5.4 atm against the coated ePTFE substrate for 60sec. The glass microscope slide containing the artery portion was thenexamined under SEM.

FIG. 10 is a representative SEM micrograph of the artery portion afterexposure for 60 sec at 5.4 atm to a coated ePTFE substrate. The“cobblestone” morphology of the endothelial layer is visible to theleft. The endothelial layer to the right is extensively covered withengaged and embedded paclitaxel crystals, indicating transfer from theePTFE substrate to the vascular tissue. The high aspect ratio of thecrystals is intact, indicating mechanical stability and mechanicalstrength of the crystals during the 60 sec compression at 5.4 atm. Allexamined ePTFE substrates of Example 1 and Example 2, coated withpaclitaxel or paclitaxel/urea according to Example 4, showed similarresults.

Example 11

This Example describes the general procedure for the preparation of drugcrystals adhered or otherwise embedded onto a substrate using vaporannealing.

The substrates on glass slides of Example 4 were inserted into a 50 mlpolypropylene centrifuge tube (VWR). 100 μl of solvent (methanol ACSgrade, ethanol 200 proof absolute grade, acetonitrile ACS grade, ordeionized water) was carefully pipetted into the tube's conical base,ensuring no contact with the glass slide, the tube tightly capped, andthe tube laid on its side such the substrate faced up. The evaporatingsolvent saturated the tube's interior atmosphere with solvent vapor.Samples were maintained in this condition for 48 hrs at about 20° C. atan ambient atmospheric pressure of about 773 mm Hg.

Example 12

This example describes the SEM visualization and orientation of drugcrystals adhered to and oriented onto the substrates of Example 1 ascoated according to Example 11.

FIGS. 11A to 11D are the SEM micrographs of paclitaxel coated frommethanol (30 mg/ml) onto ePTFE of a first microstructure comprising veryhighly elongated fibrils.

FIG. 11A is paclitaxel coated onto ePTFE without a vapor annealing step,and produced a plurality of aggregates of paclitaxel crystals comprisinghollow acicular habits. The crystals and aggregates were observed topenetrate into the ePTFE substrate, as indicated by elongated ePTFEnodes interconnected among the crystal aggregates. The aggregates wereobserved to be projecting from the ePTFE substrate at a projection angleof about 20° to about 90°.

FIG. 11B is paclitaxel coated onto ePTFE with an acetonitrile vaporannealing step, and produced a plurality of aggregates of paclitaxelcrystals comprising acicular habits. It is unclear if these habits arehollow with sealed ends or if the hollow habit was transformed into asolid habit. The crystals and aggregates were observed to penetrate intothe ePTFE substrate, as indicated by elongated ePTFE nodesinterconnected among the crystal aggregates. The aggregates wereobserved to orient relative to the ePTFE substrate at a projection angleof about 20° to about 90°.

FIG. 11C is paclitaxel coated onto ePTFE with an ethanol vapor annealingstep, and produced a plurality of aggregates of paclitaxel crystalscomprising hollow acicular habits. The crystals and aggregates wereobserved to penetrate into the ePTFE substrate, as indicated byelongated ePTFE nodes interconnected among the crystal aggregates. Theaggregates were observed to orient relative to the ePTFE substrate at aprojection angle of about 20° to about 90°.

FIG. 11D is paclitaxel coated onto ePTFE with a methanol vapor annealingstep, and produced a plurality of discrete paclitaxel crystalscomprising acicular habits. The crystals were observed to penetrate andembed into the bulk of the ePTFE substrate, as indicated by elongatedePTFE nodes interconnected among the crystals. The crystals wereobserved to orient relative to the ePTFE substrate at a projection angleof about 20° to about 90°, with many crystals also laying parallel tothe substrate surface.

FIGS. 12A to 12D are the SEM micrographs of paclitaxel coated fromacetone (30 mg/ml) onto ePTFE of a first microstructure comprising veryhighly elongated fibrils.

FIG. 12A is paclitaxel coated onto ePTFE without a vapor annealing step,and produced a smooth, continuous coating, absent of any high aspectratio habits.

FIG. 12B is paclitaxel coated onto ePTFE with an acetonitrile vaporannealing step, and produced a plurality of aggregates of paclitaxelcrystals comprising thin, irregular acicular habits. The crystals andaggregates were observed to penetrate into the bulk of the ePTFEsubstrate, as indicated by elongated ePTFE nodes interconnectedthroughout the crystal aggregates. The aggregates were observed toorient relative to the ePTFE substrate at a projection angle of about20° to about 90°.

FIG. 12C is paclitaxel coated onto ePTFE with an ethanol vapor annealingstep, and produced a plurality of aggregates of paclitaxel crystalscomprising acicular habits. The crystals and aggregates were observed topenetrate into the bulk of the ePTFE substrate, as indicated byelongated ePTFE nodes interconnected throughout the crystal aggregates.The aggregates were observed to orient relative to the ePTFE substrateat a projection angle of about 20° to about 90°.

FIG. 12D is paclitaxel coated onto ePTFE with a methanol vapor annealingstep, and produced a plurality of discrete paclitaxel crystalscomprising acicular habits. The crystals were observed to penetrate intothe bulk of the ePTFE substrate, as indicated by elongated ePTFE nodesinterconnected throughout the crystals. The crystals were observed toorient relative to the ePTFE substrate at a projection angle of about20° to about 90°.

FIGS. 13A to 13D are the SEM micrographs of paclitaxel coated frommethanol (30 mg/ml) comprising urea (8:1 mass ratio paclitaxel:urea)onto ePTFE of a first microstructure comprising very highly elongatedfibrils.

FIG. 13A is paclitaxel coated onto ePTFE without a vapor annealing step,and produced a plurality of aggregates of paclitaxel crystals comprisingacicular habits. The crystals and aggregates were observed to penetrateinto the bulk of the ePTFE substrate, as indicated by elongated ePTFEnodes interconnected throughout the crystal aggregates. The aggregateswere observed to orient relative to the ePTFE substrate at a projectionangle of about 20° to about 90°.

FIG. 13B is paclitaxel coated onto ePTFE with an acetonitrile vaporannealing step, and produced a plurality of paclitaxel crystalscomprising elongated, irregular acicular habits in a dense mat. Thecrystals were observed to penetrate into the bulk of the ePTFEsubstrate, as indicated by elongated ePTFE nodes interconnectedthroughout the crystals. The crystals were observed to orient relativeto the ePTFE substrate at a projection angle of about 20° to about 90°,with many crystals also laying parallel to the substrate surface.

FIG. 13C is paclitaxel coated onto ePTFE with an ethanol vapor annealingstep, and produced a plurality of aggregates of paclitaxel crystalscomprising acicular habits. The crystals and aggregates were observed topenetrate into the bulk of the ePTFE substrate, as indicated byelongated ePTFE nodes interconnected throughout the crystal aggregates.The aggregates were observed to orient relative to the ePTFE substrateat a projection angle of about 20° to about 90°.

FIG. 13D is paclitaxel coated onto ePTFE with a methanol vapor annealingstep, and produced a plurality of discrete paclitaxel crystalscomprising acicular habits. The crystals were observed to penetrate intothe bulk of the ePTFE substrate, as indicated by elongated ePTFE nodesinterconnected throughout the crystals. The crystals were observed toorient relative to the ePTFE substrate at a projection angle of about20° to about 90°, with many crystals also laying parallel to thesubstrate surface.

In this Example, a smooth glassy coating was transformed using vaporannealing into crystals that project from the porous substrate at aprojection angle of about 20° to about 90°.

Example 13

This example describes the SEM visualization and orientation of drugcrystals embedded and oriented onto the substrates of Example 2 ascoated according to Example 11.

FIG. 14 is the SEM micrographs of paclitaxel coated from methanol (30mg/ml) onto ePTFE of a second microstructure comprising very highlyelongated nodes interconnected by fibrils.

FIG. 14A is paclitaxel coated onto ePTFE without a vapor annealing step,and produced a plurality of aggregates of paclitaxel crystals comprisinghollow acicular habits. The crystals and aggregates were observed topenetrate and embed into the bulk of the ePTFE substrate, as indicatedby elongated ePTFE nodes interconnected throughout the crystalaggregates. The aggregates were observed to orient relative to the ePTFEsubstrate at a projection angle of about 20° to about 90°.

FIG. 14B is paclitaxel coated onto ePTFE with an acetonitrile vaporannealing step, and produced a plurality of paclitaxel crystalscomprising acicular habits. It is unclear if these habits are hollowwith sealed ends or if the hollow habit was transformed into a solidhabit. The crystals and aggregates were observed to penetrate and embedinto the bulk of the ePTFE substrate, as indicated by elongated ePTFEnodes interconnected throughout the crystal aggregates. The aggregateswere observed to orient relative to the ePTFE substrate at a projectionangle of about 20° to about 90°.

FIG. 14C is paclitaxel coated onto ePTFE with an ethanol vapor annealingstep, and produced a plurality of aggregates of paclitaxel crystalscomprising acicular hollow habits. The tips of the crystals appearedirregular. The crystals and aggregates were observed to penetrate intothe ePTFE substrate, as indicated by elongated ePTFE nodesinterconnected among the crystal aggregates. The aggregates wereobserved to orient relative to the ePTFE substrate at a projection angleof about 20° to about 90°.

FIG. 14D is paclitaxel coated onto ePTFE with a methanol vapor annealingstep, and produced a plurality of paclitaxel crystals comprisingacicular habits. It is unclear if these habits are hollow with sealedends or if the hollow habit was transformed into a solid habit. Thecrystals and aggregates were observed to penetrate into the ePTFEsubstrate, as indicated by elongated ePTFE nodes interconnected amongthe crystal aggregates. The aggregates were observed to orient relativeto the ePTFE substrate at a projection angle of about 20° to about 90°.

FIGS. 15A to 15D are the SEM micrographs of paclitaxel coated fromacetone (30 mg/ml) onto ePTFE of a second microstructure comprising veryhighly elongated nodes interconnected by fibrils.

FIG. 15A is paclitaxel coated onto ePTFE without a vapor annealing step,and produced a smooth, continuous coating with numerous cracks, embeddedinto the bulk of the ePTFE, and absent of any high aspect ratio habits.

FIG. 15B is paclitaxel coated onto ePTFE with an acetonitrile vaporannealing step, and produced a plurality of aggregates of paclitaxelcrystals comprising thin, elongated, irregular acicular habits. Thecrystals and aggregates were observed to penetrate into the ePTFEsubstrate, as indicated by elongated ePTFE nodes interconnected amongthe crystal aggregates. The aggregates were observed to orient relativeto the ePTFE substrate at a projection angle of about 20° to about 90°.

FIG. 15C is paclitaxel coated onto ePTFE with an ethanol vapor annealingstep, and produced a plurality of aggregates of paclitaxel crystalscomprising acicular habits. The crystals and aggregates were observed topenetrate into the ePTFE substrate, as indicated by elongated ePTFEnodes interconnected among the crystal aggregates. The aggregates wereobserved to orient relative to the ePTFE substrate at a projection angleof about 20° to about 90°.

FIG. 15D is paclitaxel coated onto ePTFE with a methanol vapor annealingstep, and produced a plurality of discrete paclitaxel crystalscomprising acicular habits in a dense mat. The crystals were observed topenetrate into the ePTFE substrate, as indicated by elongated ePTFEnodes interconnected among the crystals. The crystals were observed toorient relative to the ePTFE substrate at a projection angle of about20° to about 90°, with many crystals also laying parallel to thesubstrate surface.

FIGS. 16A to 16D is the SEM micrographs of paclitaxel coated frommethanol (30 mg/ml) comprising urea (8:1 mass ratio paclitaxel:urea)onto ePTFE of a second microstructure comprising very highly elongatednodes interconnected by fibrils.

FIG. 16A is paclitaxel coated onto ePTFE without a vapor annealing step,and produced a plurality of paclitaxel crystals comprising acicularhabits fused into aggregates. The crystals and aggregates were observedto penetrate into the ePTFE substrate, as indicated by elongated ePTFEnodes interconnected among the crystal aggregates. The aggregates wereobserved to orient relative to the ePTFE substrate at a projection angleof about 20° to about 90°.

FIG. 16B is paclitaxel coated onto ePTFE with an acetonitrile vaporannealing step, and produced a plurality of paclitaxel crystalscomprising elongated, irregular acicular habits in a dense mat. Thecrystals were observed to penetrate into the ePTFE substrate, asindicated by elongated ePTFE nodes interconnected among the crystals.The crystals were observed to orient relative to the ePTFE substrate ata projection angle of about 20° to about 90°, with many crystals alsolaying parallel to the substrate surface.

FIG. 16C is paclitaxel coated onto ePTFE with an ethanol vapor annealingstep, and produced a plurality of discrete paclitaxel crystalscomprising acicular habits. The crystals were observed to penetrate intothe ePTFE substrate, as indicated by elongated ePTFE nodesinterconnected among the crystal aggregates. The crystals were observedto orient relative to the ePTFE substrate at a projection angle of about20° to about 90°.

FIG. 16D is paclitaxel coated onto ePTFE with a methanol vapor annealingstep, and produced a plurality of paclitaxel crystals comprisingelongated, irregular acicular habits in a dense mat. The crystals wereobserved to penetrate into the ePTFE substrate, as indicated byelongated ePTFE nodes interconnected among the crystals. The crystalswere observed to orient relative to the ePTFE substrate at a projectionangle of about 20° to about 90°, with many crystals also laying parallelto the substrate surface.

FIGS. 17A to 17B are the SEM micrographs of paclitaxel coated fromacetonitrile (30 mg/ml) onto ePTFE of a second microstructure comprisingvery highly elongated nodes interconnected by fibrils.

FIG. 17A is paclitaxel coated onto ePTFE with a water vapor annealingstep, and produced a smooth, continuous coating on the ePTFE, absent ofany high aspect ratio habits.

FIG. 17B is paclitaxel coated onto ePTFE with an acetonitrile vaporannealing step, and produced a plurality of paclitaxel crystalscomprising elongated, irregular acicular habits in a dense mat. Thecrystals were observed to penetrate into the ePTFE substrate, asindicated by elongated ePTFE nodes interconnected among the crystals.The crystals were observed to orient relative to the ePTFE substrate ata projection angle of about 20° to about 90°, with many crystals alsolaying parallel to the substrate surface.

FIGS. 18A to 18B are the SEM micrographs of paclitaxel coated fromchloroform (30 mg/ml) onto ePTFE of a second microstructure comprisingvery highly elongated nodes interconnected by fibrils.

FIG. 18A is paclitaxel coated onto ePTFE with a water vapor annealingstep, and produced a smooth, continuous coating, absent of any highaspect ratio habits. The coating was cracked and separated, orientingand aligning the ePTFE fibrils, indicating the coating had penetratedinto the bulk of the ePTFE substrate.

FIG. 18B is paclitaxel coated onto ePTFE with an acetonitrile vaporannealing step, and produced a plurality of paclitaxel crystalscomprising acicular habits, along with numerous individual discretecrystals. The crystals were observed to penetrate into the ePTFEsubstrate, as indicated by elongated ePTFE nodes interconnected amongthe crystals. The crystals were observed to orient relative to the ePTFEsubstrate at a projection angle of about 20° to about 90°, with manycrystals also laying parallel to the substrate surface.

In this example, a smooth glassy coating was transformed using vaporannealing into crystals that project at 20-90° relative to thesubstrate.

Example 14

This example describes the preparation of a porous sample substratecomprising ePTFE of a third microstructure comprising islands of PTFE ordensified sections of ePTFE attached to and raised above an underlyingePTFE microstructure, further comprising drug crystals, wherein thecrystals occupy the underlying ePTFE microstructure. This examplefurther describes the utility of said coated substrate for the treatmentof a tissue using said drug crystals.

An ePTFE membrane was obtained comprising a 14 layer laminate, preparedas per U.S. Pat. No. 5,641,566 to Kranzler et al., incorporated hereinby reference in its entirety. The ePTFE membrane was processed using ahigh energy surface treatment comprising a plasma treatment followed bya heating step, as per U.S. Pat. No. 7,736,739 to Lutz et al.,incorporated herein by reference in its entirety. Briefly, the ePTFEmembrane was exposed to a high power atmospheric argon plasma (model#PT-2000P; Tri-Star Technologies, El Segundo, Calif.) for 3 minutes,restrained in a pin frame, then heated at 360° C. for 8 min. Arepresentative SEM micrograph showing the microstructure of this type ofePTFE membrane is shown in cross section in FIG. 20A and in plan view inFIG. 20B. Densified ePTFE regions or plateau-like structures 2002 areshown on the raised surface of the material. Below these plateau-likestructures, the node 2004 and fibril 2006 microstructure of the ePTFEunderlying material can be seen. The membrane was coated with paclitaxelcrystals, optionally containing urea excipient, according to Example 4.

FIG. 24 is an SEM image of paclitaxel coated from methanol (30 mg/ml)onto an ePTFE membrane comprising ePTFE of a third microstructurecomprising islands of PTFE or densified sections of ePTFE attached toand raised above an underlying ePTFE microstructure. Densification ofthe ePTFE to form the plateau-like structures prevented paclitaxelcrystals from adhering to the plateau-like structures 2002. Insteaddiscrete, individual crystals and crystal aggregates associated with andembedded in the underlying fibrils 2006 of the ePTFE microstructure andprojected there from the angles of about 20° to about 90°.

FIG. 25 is an SEM image of paclitaxel coated from methanol (30 mg/ml)comprising urea excipient (8:1 mass ratio paclitaxel:urea) onto an ePTFEmembrane comprising ePTFE of a third microstructure comprising islandsof PTFE or densified sections of ePTFE attached to and raised above anunderlying ePTFE microstructure. The paclitaxel/urea crystals did notadhere to the densified regions 2002. Instead discrete, individualcrystals and crystal aggregates associated with and embedded in theunderlying fibrils 2006 of the ePTFE microstructure and projected therefrom an angles of about 20° to about 90°.

FIGS. 21A-21C are schematics of the ePTFE substrate material shown inFIGS. 20A, 20B, 24, and 25, in which densified regions 2002 of ePTFE areattached to and raised above an underlying, less dense or fibrillatedePTFE microstructure illustrated with nodes 2004 and fibrils 2006, seenin FIG. 21A, further comprising drug crystals 2110, wherein the crystals2110 occupy the underlying ePTFE microstructure, and wherein the poroussubstrate is compressible in the thickness dimension whereas theprojected crystals are not compressible in their axes dimension (FIG.21B), and wherein upon compression of the porous substrate in thethickness dimension the drug crystals project from the porous substrate,as shown in FIG. 21C.

Numerous characteristics and advantages have been set forth in thepreceding description, including various alternatives together withdetails of the structure and function of the devices and/or methods. Thedisclosure is intended as illustrative only and as such is not intendedto be exhaustive. It will be evident to those skilled in the art thatvarious modifications may be made, especially in matters of structure,materials, elements, components, shape, size, and arrangement of partsincluding combinations within the principles of the invention, to thefull extent indicated by the broad, general meaning of the terms inwhich the appended claims are expressed. To the extent that thesevarious modifications do not depart from the spirit and scope of theappended claims, they are intended to be encompassed therein.

What is claimed is:
 1. A method of preparing a composite comprising aporous substrate and a drug crystal of high aspect ratio habit, suchthat the crystals are at least partially extending into the substrateand are projected from substrate at an angle of about 20 to 90 degreeswith respect to the substrate and comprising the steps of preparing asolution of drug in the organic solvent, wherein the organic solvent iscapable of wetting the substrate; applying the solution to the poroussubstrate; and causing the solvent to evaporate to form the drugcrystal.
 2. The method of claim 1, wherein the substrate comprises anode and fibril microstructure.
 3. The method of claim 1, wherein thesubstrate comprises ePTFE.
 4. The method of claim 1, wherein the drugcomprises paclitaxel.
 5. The method of claim 1, wherein the drug crystalis a hollow, acicular crystal.
 6. The method of claim 1, wherein theorganic solvent comprises methanol.
 7. The method of claim 1, furthercomprising the step of treating the composite with at least one ofsolvent annealing, vapor annealing, and thermal annealing.
 8. The methodof claim 1, wherein applying the solution comprises at least one ofpipetting, dipping and spraying.
 9. The method of claim 1, furthercomprising the step of applying a non-solvent, wherein the non-solventcomprises at least one of water, and ethyl acetate.
 10. The method ofclaim 1, wherein the porous substrate forms a surface of a medicaldevice.
 11. The method of claim 10, wherein the medical device is acatheter-based device.
 12. A method of treating a disease locallycomprising the steps of radially expanding medical device from a firstdiameter to a second diameter, wherein the medical device comprises asubstrate and the substrate contacts a tissue upon expansion and whereinthe substrate comprises a polymeric substrate comprising a plurality ofhigh aspect ratio paclitaxel crystals that at least partially projectfrom the substrate at an angle of at least 20 to 90 degrees relative tothe substrate and at least partially extend into the substrate.
 13. Themethod of claim 12, wherein the substrate comprises an excipient. 14.The method of claim 12, wherein at least a portion of the plurality ofhigh aspect ratio paclitaxel crystal penetrates the tissue.
 15. A drugcrystal comprising paclitaxel having a hollow crystal habit.
 16. Thedrug crystal of claim 15, wherein the hollow crystal habit is acicular.17. The drug crystal of claim 15, wherein the hollow crystal habit atleast partially filled with another material.
 18. The drug crystal ofclaim 15, wherein the drug crystal is located on the surface of amedical device.
 19. A method of making a drug delivery device having asubstrate comprising applying a solution comprising paclitaxel and anorganic solvent to the substrate; allowing paclitaxel to crystallizethrough evaporation of the solvent, wherein the substrate comprises apolymer having a node and fibril microstructure and wherein the organicsolvent is capable of wetting the node and fibril microstructure. 20.The method of claim 19, wherein the polymer comprises ePTFE.
 21. Themethod of claim 19, wherein the organic solvent comprises at least oneof methanol and ethanol.
 22. A method of making a drug delivery devicehaving a substrate comprising the steps of applying a solutioncomprising paclitaxel to a substrate; causing the paclitaxel tocrystallize; and. exposing the paclitaxel to a vapor phase solvent tocause the paclitaxel to form acicular crystal habits that project fromthe surface at an angle of between 20 to 90 degrees.
 23. The method ofclaim 22, wherein the vapor phase solvent comprises at least one ofacetonitrile, methanol, and ethanol.
 24. A method of preparing at leastone drug crystal of high aspect ratio habit comprising the steps ofpreparing a solution of drug in the organic solvent, wherein the organicsolvent is capable of wetting the substrate; applying the solution tothe porous substrate; causing the solvent to evaporate to form the atleast one drug crystal; and removing the at least one drug crystal fromthe substrate.
 25. The method of claim 24, wherein said at least onehigh aspect ratio habit crystal comprises paclitaxel.
 26. The method ofclaim 25, wherein said paclitaxel comprises hollow acicular paclitaxel.27. The method of claim 26, further comprising filling the lumen of saidat least one hollow acicular paclitaxel drug crystal at least partiallywith a second material.